JPS63139216A - Oil surface detection system - Google Patents

Abstract

PURPOSE:To exclude errors due to the thermal diffusion coefficient of a temp.-sensitive element, by allowing the temp.-sensitive element to generate heat itself not only in the case of obtaining threshold value but also in the case of obtaining a comparing value. CONSTITUTION:At first, temp. is detected at a b-point. That is, the voltage VP at a P-point is converted to a digital value by an A/D converter 7 to be stored in RAM 9. When this detected temp. is the first one, the measurement of a time T2 is started and a transistor (TR) 4 is turned ON to allow a temp.-sensitive element 1 to begin to generate heat itself and the heat self-generation temp. of the temp.-sensitive element 1, that is, the voltage VP at the P-point to be converted to a digital value by the A/D converter 7 and predetermined operation is performed to convert said digital value to a threshold value. next, this threshold value is stored in RAM 9 and the measurement of a time T1 is started and, during this time, TR 4 is turned OFF to finish the self-generation of heat. After the elapse of the time T1, the same operation as that performed heretofore is performed and, when it is judged that the detected temp. is not the first one, the measurement of the time T2 is started and TR 4 is turned ON to allow the element 1 to start the self-generation of heat. After the waiting of the time T2, the voltage VP at the P-point, that is, the self-generation heat temp. is detected at an a-point to be converted to a digital value by the A/D converter 7 and this comparing value is compared with the threshold value previously stored. For example, when threshold value > comparing value is formed, it is judged that there is no oil.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention utilizes a temperature-sensitive element made of gold having temperature-resistance characteristics, and utilizes the difference in heat dissipation coefficient between the temperature-sensitive element in air and oil. For example, the present invention relates to an oil level detection method for detecting the position of the oil level in a compressor used in a refrigerator.

[Conventional technology]

FIG. 3 is a circuit diagram for explaining a conventional oil level detection method. In the figure, reference numeral 1 is placed at the oil level detection position, has a predetermined resistance-temperature characteristic t, and is a companion such as a thermistor that generates pressure according to the reference temperature and the temperature at the time of self-heating. Temperature sensing element 2 is connected in series with temperature sensing element 1 between the power supply vCC and ground and is used as a reference! The first voltage dividing resistor 3 is connected between the voltage dividing point P and the collector of the transistor 4 and is used during self-heating. 4 is the transistor whose emitter is connected to the power supply Vec K. , 5 is a nine microcomputer consisting of elements indicated by numerals 6 to 10.

6 is connected to the transistor 40 pace and the next output device, 7
is connected to the voltage dividing point P, and converts the output voltage vp of the temperature sensing element 1, which is affected by the voltage at the P point, from analog to digital.
Digital converter (hereinafter referred to as converter), 8t
i calculation unit, 9 random access memory (RAM), 1
0 is read-on memory (ROM).

Next, the operation will be explained. Figure 4 shows the timing of the reference temperature detection time and the temperature detection time during self-heating, where T is the recovery time from the self-heating state to the reference temperature, and T is the time required for self-heating. . While the output device 16 of the microcomputer 5 outputs a %HI level signal, the transistor 4 is OFF and the temperature sensitive cable 1 recovers to the reference temperature. The reference source Ql is detected at point b in FIG. , stored in RAMQ.

Next, time T! A signal of %L level is output from the output device 6 of the microcomputer 5 only during this period, and during this period, the transistor 4 is not ON, and a large current flows through the temperature sensing element 1 through the voltage dividing resistor 3. self-heats. In this state, at point a at the end of time T, the voltage Vp at point P
is digitized by the A/D converter 7 and taken into the calculation section 8. The calculation unit 8 compares this comparison value with the above-mentioned threshold value stored in the RAM 9, and determines the presence or absence of oil-dried hot water.

[Problem that the invention seeks to solve]

As described above, the conventional oil level detection method detects the reference temperature from the temperature sensing element 1 when no self-heating is occurring, and determines the threshold value based on this detection voltage. Although this has nothing to do with the heat dissipation coefficient during self-heating, the comparison value compared with this threshold value is obtained by detecting the temperature from temperature-sensitive cord 1 during self-heating, so the heat dissipation coefficient of temperature-sensitive cord 1 The relationship between the magnitude and the threshold value may be reversed, leading to problems such as incorrect judgments.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide an oil level detection method that can eliminate errors in the heat dissipation coefficient during self-heating of the temperature sensing element.

[Elaborate means to solve problems]

The oil level detection method according to the present invention causes a temperature sensing element having a predetermined temperature-resistance characteristic to self-heat in order to obtain a threshold value for detecting the presence or absence of oil.

[Effect]

The oil level detection method in this invention causes the temperature sensing element to self-heat and obtains the threshold II based on the temperature, so that r:
Since the A value is dependent on the heat dissipation coefficient of the temperature sensing element, the comparative digital value also has a reduced dependence on its heat dissipation coefficient due to self-heating, and when comparing these two values, there is an error due to the influence of the heat dissipation coefficient. Try to remove your friend.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Since the node/ware according to an embodiment of the present invention is the same as the circuit shown in FIG. 3, this figure will be referred to, and FIG. It is built into the ROM10 shown in FIG. 3 and executed by the arithmetic unit 8.

Next, the operation will be explained. The recovery time for the temperature sensing element 1 to reach the reference temperature from self-heating, and the time T2 required for self-heating are shown in FIG. 4 and are the same as those of the conventional one. Detects temperature. That is, in step 20, the voltage vp at point P is taken into the converter 7, and in the next step 21, A/D conversion is performed using the A/D converter 7 to digitize it, and in the next step 22
This digital value is stored in t-RAMQ. This R.A.
In step 23, it is determined whether the digital value stored in the MQ is the first time, that is, whether the detected temperature is the first time.

If it is the first temperature, the time T is set in the next step 24.
, starts measuring transistor 4? Turn it on to start self-heating of the temperature sensing element 1. In step 25, the system waits until the time Tt has elapsed, and after waiting, in the next step 26, the self-heating temperature, that is, the voltage Vp at point P is detected, and the A/
The data is taken into the D converter 7, and in the next step 27, it is A/p converted by the A filter converter 7 to become a digital value, and in step 28, a predetermined calculation is performed based on this digital value to convert it into a threshold value. In step 29, this threshold value is stored in RAMe, and in the next step 30, the measurement of time Ti is started. During this time, the transistor 4 is turned off to end the self-heating at Stella 7" 31, and in step 32, the process waits until time T1 has elapsed. do.

After time T has elapsed, return to step 20, and step 20~
The same operation as above is performed up to step 22, and in step 23 a negative judgment is made that it is not the first temperature, and then step 3
Move on to 3.

In step 33, measurement of time T is started, and in next step 34, transistor 4fc is turned on to start self-heating of temperature sensing element 1, and in step 35, the process waits until time T has elapsed. In time! After waiting, in step 36, the voltage vp at point P in FIG. Execute. Next, step 3
In step 8, this A/D converter is stored in the RAM 9 together with a comparison value, and the magnitude is compared with the above threshold value. For example, if the threshold value is greater than the comparison value, the process proceeds to step 42 where it is determined that there is no oil, and if the threshold value is less than the comparison value, the process proceeds to step 39 where it is determined that there is oil.

If it is determined that there is no oil, a detailed control signal to operate the oil-free relay is output in step 42, and the series of operations is completed.

If it is determined that there is oil, time T is reached in step 39.

The measurement of transistor 4 is started, and in step 40, the transistor 4 is
jtOFF, the self-heating of the temperature sensing element 1 is ended, and in step 41, the process waits until time T+ has elapsed. After waiting for the time TI, the process returns to the next step 20 and repeats the above operation.

In addition, the nine threshold values obtained in the above operation were obtained at point a, but there are also other values, since the initial passage of temperatures with different diameters during the self-heating time T is a short period from the initial startup. The trough may be determined based on the trough partial pressure value when the resistor 1 is present in oil. Also, a certain period of time, for example, time T! If the heat dissipation coefficient of the temperature sensing element 1 is determined from the self-heating temperature data corresponding to other temperatures,
The threshold value for that temperature is determined in accordance with the processing by the program stored in the ROM10 in advance. The nine threshold values determined above will be used without change thereafter.

The diagram for the second factor shows the pressure in the thermistor's range with respect to the temperature at the time of self-heating when an NTC thermistor is used as the temperature sensing element 1, and the line iLt is L when the thermistor is in oil.
*When the Fi thermistor exists in the air, L indicates each threshold value determined from the value at the initial passage of each temperature. As is clear from this figure, at each temperature point, the voltage value of L+ (in oil) and the voltage value of L8 (threshold value)>L! voltage value (in air without oil).

In the above embodiments, the self-heating time t' Tt is common, but may be different.

〔Effect of the invention〕

As described above, according to the present invention, the thermosensor is made to self-heat both when obtaining a threshold value and when obtaining a comparison value, so that the error due to the heat dissipation coefficient of the thermosensor itself affects both fiii. It is removed during comparison, which has the effect of preventing malfunctions due to errors and obtaining highly accurate results.

[Brief explanation of the drawing]

FIG. 1 is an operation flow diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a circuit diagram showing the oil detection device, and FIG. 4 is a timing diagram showing the self-heating time and the recovery time to the reference temperature. In the figure, 1...sensor m resistor, 2, 3... voltage dividing resistor, 4...
...Transistor, 6...Output device, 7...A/p
Converter, 8... Arithmetic unit, 9... RAM%lO...
ROM. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A temperature sensing element disposed at an oil level detection position and having a predetermined resistance-temperature characteristic, a heating means for causing the temperature sensing element to self-heat by energization, and a temperature of the temperature sensing element as a temperature of the temperature sensing element. and an analog/digital converter that digitizes the voltage, and obtains a threshold value for detecting the presence or absence of oil based on a reference digital value corresponding to the temperature of the temperature sensing element within a first time interval; An oil level detection method that detects the presence or absence of oil by obtaining a comparison digital value corresponding to the temperature of the temperature sensing element during self-heating within the time interval of 2, and comparing the magnitude of the comparison digital value with the threshold value. An oil level detection method characterized in that the temperature sensing element self-heats within the first time interval.